After updating our work computers to the newest available update from Apple (MacOS Sierra Version 10.12.5) my InDesign CS6 program runs incredibly slowly, freezes and crashes regularly deeming it impossible to get through all of my tasks throughout the day. Photoshop and Illustrator are running smoothly.

I've read multiple forums to try and fix this issue and nothing has worked thus far. I've also read that the new update is not compatible with the CS6 programs, but this is simply not true as the other two computers in the office that were updated, utilise the same programs and are running fine - as they did before.

I've also read that the new update is not compatible with the CS6 programs, but this is simply not true as the other two computers in the office that were updated, utilise the same programs and are running fine - as they did before

It's a crapshoot, Debbie. CS6 has long since reached end of life—meaning Adobe stopped updating it few years before Sierra was released in the fall of 2016. If it happens to work, great. If not, there is nothing Adobe will do for you.

If you really need CS6 to run on that computer, consider rolling back the OS. Looking ahead, if you don't want to upgrade your software, refrain updating your operating system.